Purification of zinc solutions



v Solutions,

UNITED STATES PATENT OFFICE.

HENRY LIVINGSTONE SULMIAN AND SAMUEL FIELD, or LONDON, ENGLAND,

ASSIGNORS 'ro THE METALS EXTRACTION CORPORATION, LIMITED, or LON- DON,ENGLAND.

No Drawing.

To (115 whom it may concern:

land, have invented certain new and useful Improvements in thePurification of Zinc fication.

refers more particularlyto the purification Y of zinc sulfate solutionsobtained by the treatment of zmc'ores orzmc-contammg electrolytically.

materials with sulfuric acid, from which solutions the zinc issubsequently deposited As is well-known, to obtain a successfuldeposition of zincby electrolysisthe zinc sulfate liquors must) be of ahigh order of purity; impurities, such as copper, cadmium,

iron, antimony, arsenic, nickel and-cobalt,

' musthe'eliminated or substantially so, as

"they affect adversely a'nd'very seriouslythe deposition bothqualitatively and quantitatively. For example it is desirable thatnickel be reduced to a-quantity of the order arsenic and antimony iscommonly effected 30,

that more difiiculty is experienced in the rev nioval of cobalt andnickel, and the presentof one-half to one part per million of liquor.

The elimination of iron, copper, cadmium,

with comparative ease, but it has been found invention relatesparticularly to the purifi "cation of zinc solutions from thesenmetals.

For'the removal of copper, cadmium, and

-, T'similar very 'electro-negative metallic impurities, tube millingwith zinc balls or agitating the solutions with zinc dust is usuallyfound efiective, and the methods employed 40 for removing iron alsoresult in the simul- Qtaneous removal of arsenic and antimony whenpresent."

' moved by zinc dust, and further wjefind that [nickel-is not completelyremoved orto'the degree whichrenders electrolytic zinc depositio'neconomically possible, by zinc dust unless the solutions treated are ina warm According to the present condition, as for example at atemperature of from 80 to 100 C.

T Specification of Letters Patent.

of which-the following is a speciinvention, there- Patented M ay'25,1920.

Application filed May 12, 1918. Serial No. 296,552.

fore, a process for the purification of zinc solutions, such for exampleas zinc sulfate solutions, from nickel consists in treating thesolutions with zinc in a form presenting a large surface, such as zincfume or blue powder, at a tem erature of, for example, from 80 to 100The zinc employed, such as fume or blue powder, is preferably firstwashed with acid for the purposeof removing oxid and rendering itsaction more eflicacious.

In carrying the present invention into effect to obtain a pure solutionof zinc sul-- fate from ores or Zinc-containing materials for thesubsequent electro-deposition of the zinc, the zinc ore orzinc-containing material, roasted if necessary, is treated with the acidliquors from the electrolytic cells in which zinc has been deposited,and from thesolution thus obtained any iron, arsenic, antimony, copperand cadmium present are first removed; The solutions are then placed ina vessel having means to stir or agitate them gently,-such for exampleas apaddle,

and means to heat them, as for example pipes arranged in the vesselfed'with waste steam. It is usually found desirable to provide baffiesin the vessel so as to prevent the liquid swirling around withoutrelative motion of the finelygdivided zinc and the solu' tion. To thesolutions isadded a quantity of zinc {fume which has fbeen previouslywashed with sulfuri "old, and they are heatedto a temperature of from 80C. to

- 100 C. and are gently stirred, whereby the nickel present isprecipitated, andwith it any traces "of copper and cadmium which mayhave remained after the tube milling with zinc balls. An equivalent ofzinc passes into solution.

When zinc fume is employed a'quantity a of about 1 part to 200 parts'of'liquor usually gives a satisfactory result, and as the nickel .isordinarily present only at the rate of 10 to 20 parts per million ofsolution, this quantity constitutes a large excess over thattheoretically necessary for the removal ofthe nickel.

The zinc fume can be used several times The partly spent while the smalladdition of fresh powder serves to remove the last traces more rapidly.

described in our co-pending application No. 296,553, filed May 12, 1919and entitled Imi provements in the purification of zinc solu tions.

By the process described above zinc' liquors containing nickel in anamount suifi-f,

cient to render the electrolytic extraction of zinc impracticable, arepurified to a high degree, the quantity of nickel remaining in solutionamounting to one-half part per 'millionor even less. 7 r

e What We claim as our invention and deshe to secure by Letters Patentis 1. A process for the purification of zinc solutions from nickel,which consists in treating the solution, freed from iron, arse-f nic,antimony, copper and cadmium, with finely divided zinc withapplicationof heat. 2. A process for the purification of zinc sulfate solutionsfrom nickel, which consists in treating the solution, freed from iron,arsenic', antimony, copper and cadmium, with finely divided zinc at atem-q perature of to C.

3". A process for the purification ofjzinc sulfate solutions fromnickel, which-consists in treating the solution, freed from, 1ron,arsenic, antnnony, copper and cadm1um, w1th ZlIlC fume, at atemperature-of" 80? to 100 C.

4. In the purification after removal of iron, arsenic,, antimony,

' copper and cadmium, washing the zinc with acid to revivify it forre-use. V

In testimony whereof We have signed ournames to this specification 1nthe presence -0ftwo subscribing witnesses.

HENRI LIVINGSTONE SUIiMAN.

- s m an FIELD.

Witnesses! i H. N. RIEDY,

A, W. SHEPHERD. -v

of zinc solutions from nickel by treating the solution; with zinc in aform presenting a: large surface,

